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 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
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package javax.swing;

import java.awt.event.*;
import javax.swing.event.*;


/**
 * A model for a potentially unbounded sequence of object values.  This model
 * is similar to <code>ListModel</code> however there are some important differences:
 * <ul>
 * <li> The number of sequence elements isn't necessarily bounded.
 * <li> The model doesn't support indexed random access to sequence elements.
 * Only three sequence values are accessible at a time: current, next and
 * previous.
 * <li> The current sequence element, can be set.
 * </ul>
 * <p>
 * A <code>SpinnerModel</code> has three properties, only the first is read/write.
 * <dl>
 * <dt><code>value</code>
 * <dd>The current element of the sequence.
 *
 * <dt><code>nextValue</code>
 * <dd>The following element or null if <code>value</code> is the
 * last element of the sequence.
 *
 * <dt><code>previousValue</code>
 * <dd>The preceding element or null if <code>value</code> is the
 * first element of the sequence.
 * </dl>
 * When the the <code>value</code> property changes,
 * <code>ChangeListeners</code> are notified.  <code>SpinnerModel</code> may
 * choose to notify the <code>ChangeListeners</code> under other circumstances.
 *
 * @author Hans Muller
 * @see JSpinner
 * @see AbstractSpinnerModel
 * @see SpinnerListModel
 * @see SpinnerNumberModel
 * @see SpinnerDateModel
 * @since 1.4
 */
public interface SpinnerModel {

  /**
   * The <i>current element</i> of the sequence.  This element is usually
   * displayed by the <code>editor</code> part of a <code>JSpinner</code>.
   *
   * @return the current spinner value.
   * @see #setValue
   */
  Object getValue();


  /**
   * Changes current value of the model, typically this value is displayed
   * by the <code>editor</code> part of a  <code>JSpinner</code>.
   * If the <code>SpinnerModel</code> implementation doesn't support
   * the specified value then an <code>IllegalArgumentException</code>
   * is thrown.  For example a <code>SpinnerModel</code> for numbers might
   * only support values that are integer multiples of ten. In
   * that case, <code>model.setValue(new Number(11))</code>
   * would throw an exception.
   *
   * @throws IllegalArgumentException if <code>value</code> isn't allowed
   * @see #getValue
   */
  void setValue(Object value);


  /**
   * Return the object in the sequence that comes after the object returned
   * by <code>getValue()</code>. If the end of the sequence has been reached
   * then return null.  Calling this method does not effect <code>value</code>.
   *
   * @return the next legal value or null if one doesn't exist
   * @see #getValue
   * @see #getPreviousValue
   */
  Object getNextValue();


  /**
   * Return the object in the sequence that comes before the object returned
   * by <code>getValue()</code>.  If the end of the sequence has been reached then
   * return null. Calling this method does not effect <code>value</code>.
   *
   * @return the previous legal value or null if one doesn't exist
   * @see #getValue
   * @see #getNextValue
   */
  Object getPreviousValue();


  /**
   * Adds a <code>ChangeListener</code> to the model's listener list.  The
   * <code>ChangeListeners</code> must be notified when models <code>value</code>
   * changes.
   *
   * @param l the ChangeListener to add
   * @see #removeChangeListener
   */
  void addChangeListener(ChangeListener l);


  /**
   * Removes a <code>ChangeListener</code> from the model's listener list.
   *
   * @param l the ChangeListener to remove
   * @see #addChangeListener
   */
  void removeChangeListener(ChangeListener l);
}
